By the way I am using PowerStore 1. Here is the the config:
//Shipping Settings
$WAGLOBAL_Shipping_Enabled = true;
$WAGLOBAL_USPS_User = "XXXXXXXXXXX"; // get this when you sign up for API access
$WAGLOBAL_USPS_Server = "http://production.shippingapis.com/ShippingAPI.dll"; // change this to the live server when you go live